from StringIO import StringIO
import struct

from google.appengine.api import images

from Img import NotSupportedImageEncodingError
  
def getImageInfo(data):
   data = str(data)
   size = len(data)
   height = -1
   width = -1
   content_type = ''

   # handle GIFs
   if (size >= 10) and data[:6] in ('GIF87a', 'GIF89a'):
       # Check to see if content_type is correct
       content_type = 'image/gif'
       w, h = struct.unpack("<HH", data[6:10])
       width = int(w)
       height = int(h)

   # See PNG 2. Edition spec (http://www.w3.org/TR/PNG/)
   # Bytes 0-7 are below, 4-byte chunk length, then 'IHDR'
   # and finally the 4-byte width, height
   elif ((size >= 24) and data.startswith('\211PNG\r\n\032\n')
         and (data[12:16] == 'IHDR')):
       content_type = 'image/png'
       w, h = struct.unpack(">LL", data[16:24])
       width = int(w)
       height = int(h)

   # Maybe this is for an older PNG version.
   elif (size >= 16) and data.startswith('\211PNG\r\n\032\n'):
       # Check to see if we have the right content type
       content_type = 'image/png'
       w, h = struct.unpack(">LL", data[8:16])
       width = int(w)
       height = int(h)

   # handle JPEGs
   elif (size >= 2) and data.startswith('\377\330'):
       content_type = 'image/jpeg'
       jpeg = StringIO(data)
       jpeg.read(2)
       b = jpeg.read(1)
       try:
           while (b and ord(b) != 0xDA):
               while (ord(b) != 0xFF): b = jpeg.read
               while (ord(b) == 0xFF): b = jpeg.read(1)
               if (ord(b) >= 0xC0 and ord(b) <= 0xC3):
                   jpeg.read(3)
                   h, w = struct.unpack(">HH", jpeg.read(4))
                   break
               else:
                   jpeg.read(int(struct.unpack(">H", jpeg.read(2))[0])-2)
               b = jpeg.read(1)
           width = int(w)
           height = int(h)
       except struct.error:
           pass
       except ValueError:
           pass

   return content_type, width, height

def thumbnailimage(image):
    content_type, width,height = getImageInfo(image)
    if not content_type:
        raise NotSupportedImageEncodingError
    pic = images.Image(image)
    if width>height:
        pic.resize(width=160,height=160*height/width)
    else:
        pic.resize(width=160*width/height,height=160)
    pic.im_feeling_lucky()

    return pic.execute_transforms(), content_type

    
